Fluid conduits, such as a suction conduit and a water feed or air feed conduit, are provided in an endoscope for the purpose of ensuring a field of view when the inside of a body cavity is observed. When endoscopic inspection or trans-endoscopic operation is performed, a patient's blood, mucus, secretion, etc. may pass through such conduits. Further, these liquids may flow back to and enter a conduit from an opening at a leading end of the endoscope, or these liquids may remain in a conduit even after inspection. For this reason, liquids adhering to the internal wall of a conduit are cleaned by a cleaning brush for the endoscope.
The cleaning brush for the endoscope is composed of a long and flexible shaft to be inserted into a conduit of the endoscope, and a brush part provided at a leading end of the shaft. Although the internal diameter of conduits of an endoscope varies depending on types of endoscopes or types of conduits, it takes time and effort to use a plurality of different brushes according to internal diameters. Thus, conduits having various diameters are cleaned by using one brush capable of cleaning conduits ranging from a conduit having a maximum diameter to a conduit having a minimum diameter.
A conventional cleaning brush 100 is shown in FIG. 11. As for a brush part 101 of this cleaning brush 100, a plurality of resinous brush bristles 102 are arranged, and then, interposed, and twisted between metallic strands 103, whereby the brush bristles 102 are planted so as to form a cylindrical shape as a whole. A leading tip 104 made of resin is attached to a leading end of the brush part 101. A trailing end of the strand 103 is fixed to a shaft 105 by being screwed into a leading end of the shaft. Further, Patent Document 1 described below discloses a cleaning brush for an endoscope having a linear support made of a single wire, and a brush part provided at a trailing end of the linear support.    Patent Document 1: Japanese unexamined patent application, First Publication, No. 11-169334
When the conventional cleaning brush 100 shown in FIG. 11 is inserted into a conduit 106 having a small internal diameter close to the external diameter of the shaft 105, the brush bristles 102 are bent down along the internal wall of the conduit 106. For this reason, some of the brush bristles 102 are bent toward a side face of the leading end of the shaft 105, and then overlap the side face of the leading end of the shaft 105. The external diameter of this overlapping portion has a maximum value obtained by adding the external diameter of the shaft 105 and twice the external diameter of the brush bristles 102. This value may exceed the internal diameter of the conduit 106. If the cleaning brush 100 continues to be inserted in such a state, problems occur in that insertion is not allowed and insertion resistance is large.
If the shaft 105 is made thin in order to prevent the above problems, the strength of the shaft 105 declines, and when the shaft 105 is gripped and inserted into the conduit 106, the shaft 105 is apt to be buckled. Further, when the shaft 105 is gripped and inserted by a person's fingers, a problem occurs in that the contact area between the shaft 105 and the fingers may become small, and the fingers are apt to slip.
If the brush bristles 102 are made thin in order to prevent the above problem, a repulsive force when the brush bristles 102 hit the internal wall of the conduit 106 will decrease, and the capability of removing stains will decline.
In order to keep the brush bristles 102 from overlapping the side face of the shaft 105 even if the brush bristles 102 are bent, increasing the distance between the leading face of the shaft 105 and the brush bristles 102 is also conceivable. However, the strand 103 which fixes the brush bristles 102 is hard compared to the flexible shaft 105. When the length of this hard part increases, there is a problem in that it is difficult to pass the brush part 101 through endoscope conduits 106 which are complicated and have a small radius of curvature.